1. Field of the Invention
The invention relates to ramp units for floating pontoons that can be folded into a W-shape and are combined to form floating bridges (pontoon bridges) or ferries. The ramp unit comprises essentially two inner float bodies, two outer float bodies, connecting hinges between the inner float bodies, double-jointed hinges between the inner and outer float bodies, and a folding and unfolding mechanism. The driving deck formed by the upper decks of the inner and outer float bodies is planar.
2. Description of the Related Art
Floating pontoons with two inner and two outer float bodies, which are folded into a W-shape in the transport position, float on the water and provide a driving deck in their operating position, have raised sidewalks and, optionally, raised wash plates, have been known for a long time. Originally developed by the Soviet army, they are currently widely used in many Western armies. The transport of the individual floating pontoons is carried out by means of trucks. The loading surface of the trucks is provided with four rolls on which the pontoon is rolled into the water. For returning the pontoon from the water onto the truck, a hydraulically actuated crane is provided.
The folding and unfolding of the floating pontoons is realized essentially by a suitable distribution of the gravity and buoyancy centers of the inner and outer float bodies and is assisted by a folding and unfolding mechanism comprised of levers and cable pulls.
For assembling ferries and floating bridges, several floating pontoons are coupled to one another. Their ends are provided with special ramp units having a height which tapers in a wedge shape in the direction toward the bank so that vehicles can drive onto the ferry or floating bridge more easily. These ramp units are the object of the present invention.
A ramp unit has been known for some time now in the prior art in which the height reduction is achieved in that the upper deck of the inner and outer float bodies forming the driving deck is angled downwardly. Movable ramp plates or stationary tapered ramp edges are provided as drive-up aids for vehicles at the front end of the ramp unit. The lower decks of the ramp unit are unchanged. When the lower deck of the ramp unit rests on the bank or shore of a body of water, a relatively steep angle between the upper deck of the ramp unit and the upper deck of the adjacently positioned floating pontoon results. Vehicles whose chassis is not specially adapted can thus be damaged when driving across this angled driving deck area. Even all-terrain vehicles must drive at reduced speed across this angled driving deck, and this results in a reduction of the vehicle transfer rate of the pontoon bridge or ferry.
In addition to the above described older floating pontoon system, a more recent system is known in which the upper deck of the ramp unit is without angled portion, i.e., is planar over its entire length. Instead, the lower deck is angled. However, this causes several significant disadvantages.
A first disadvantage is that, when used on a flat bank, the lower angled edge rests on the bank, while the leading end of the ramp is exposed and freely suspended in the air. Accordingly, driving onto the ramp is difficult for vehicles. Furthermore, the freely exposed ramp end provides leverage which transmits the weight of a vehicle driving onto the ramp so unfavorably onto the adjacently positioned floating pontoon that the latching parts provided thereat can be overloaded.
A further disadvantage becomes apparent when the ramp unit is placed onto the truck in the transport position. Due to the angled edge at the lower deck the outer contours taper toward the leading ramp end. This configuration prevents the transport of such ramp units on standard trucks because they are only provided with four rollers. In order to be able to transport such ramp units, the trucks must be provided with additional auxiliary rolls. This is unsatisfactory.
The third disadvantage also becomes apparent in the folded transport state of the ramp unit on the transport truck. The transport latching devices provided for securing the standard floating pontoons on the truck during transport cannot be used because they cannot reach the tapered outer floating body. It is therefore necessary to provide an additional latching mechanism. This is also extremely unsatisfactory.